osCommerce – Which Version?

There are many versions of osCommerce in use today:  MS2.2, RC2a and 2.3.  Which should you use?
If you are still using MS2.2 or RC2a then provided you have patched any security issues and kept the underlying platform up to date (php V5, MySQL V5) then you are doing all the right things and you do not need to upgrade.
If you want to consider upgrading then there are two things to consider:
1. Design Impact
osCommerce 2.3  uses a grid framework for template (a.k.a. skin, theme, design) integration.  So unless your design is already based on a grid there might be slight changes to be made to integrate it into 2.3. For example the site width will need to be fixed to a certain size.  960 pixels to cater for iPads is the standard these days.
2.  Customizations
If you have customized your functionality in any way these customizations would need to be redone.  This can be a costly exercise.  So again unless you have a sound business reason for the upgrade, don’t bother.  Number #1 rule, don’t let technology drive the decision.
A lot of developers will advise you to move away from osCommerce and convert your site to Magento Community Edition or Prestashop or even a rent by the month solution.  They mainly tell you this because they do not work osCommerce but want your business.  They often say osCommerce is insecure hoping to scare you into making a decision based on technology rather than business.
Again provided you have applied the few patches that have been released for your version and are using a secure hosting environment and you keep the underlying platform up to date  then there are no security issues and your site should be hack proof.
If you are in any doubt we can do a security audit for you.